(i) Field of the Invention
The present invention relates to a thermosetting resin composition which is excellent in heat resistance, mechanical strength, electrical insulating properties, workability and productivity, and it also relates to a laminate plate for a semiconductor substrate in which the above thermosetting resin composition is used.
(ii) Description of the Prior Art
Heretofore, thermosetting resins having an imide structure are excellent in electrical insulating properties, heat resistance, dimensional stability of molded articles and the like, and therefore they have widely been used.
A thermosetting resin obtained by thermally polymerizing an aromatic bismaleimide alone, which has typically been used is a material having excellent heat resistance, but inconveniently, it is very brittle and poor in flexibility. As a technique for overcoming such drawbacks, it has been attempted to use a thermosetting resin composition comprising an aromatic bismaleimide and an aromatic diamine. For example, a polyaminobismaleimide resin comprising N,N'-4,4'-diphenylmethanebismaleimide and 4,4'-diaminodiphenylmethane (trade name Kelimide, made by Rhone-Poulenc) has been put to practical use, and it has widely been used in varnishes for impregnation, laminate plates, molded articles and the like. In this type of thermosetting resin, however, impact resistance and flexibility are never satisfactory.
On the other hand, ceramics have exclusively been used as semiconductor substrates, but since the ceramics have a high dielectric constant, their electrical response velocity is limited, so that a wiring density cannot be increased, which interferes with the miniaturization and the weight reduction of electronic devices. Thus, the development of semiconductor substrates made of the resins has strongly been desired. However, in the case that the above thermosetting resin composition is used for the preparation of the semiconductor substrates, the storage stability of the varnishes is poor, and the heat stability of the thermally set resin substrates and electric properties such as an inductive tangent are insufficient. Hence, the further improvement of the thermosetting resin composition has strongly been desired.
In order to solve the above problems, the present applicant has already disclosed a thermosetting resin composition comprising a novel polymaleimide resin and a specific aromatic amine resin and a thermally curable resin obtained by using the same in Japanese Patent Application Laid-open No. 172324/1991. As a result of further detailed investigation, however, it has been apparent that prepregs and green sheets (which are the sheets obtained by coating films with a varnish containing a filler, subjecting them to a heat treatment so as to vaporize and remove a solvent, and then peeling) made of this combination material alone are poor in flexibility, and so the operativity of continuously molding and winding the sheet as well as productivity low. Hence, its improvement has strongly been desired. Particularly in the case of the green sheets, a winding performance must be good for a high productivity, but the winding operation has been impossible, because the molding products using the thermosetting resin composition has no flexibility.